My only advice is that you need to understand that you either DECIDE to stop snooping and doing the other things that show you are still focused on him now, or it will be stopped in the future because he won't be someone you either can or should check up on.
What I mean is that when you ask how to stop, the answer is simple; just stop. It's that simple, and really, there is no other way to do it. There is no substitute, no patch you can put on to stop the cravings. You have to want to know more about yourself than you do him and when that happens, you will begin to understand why snooping is not really what you need to do. What he is doing is irrelevant to what you are doing or what you need to do. Either you choose to detach on your own or detachment will end up your only option.
When/if he decides to give up this lifestyle and come back to you, you need to be in a position where you can judge his sincerity and decide if you want to give your M another chance. Right now, that is not possible so just turn your attention on you and forget his goings on.
